Humans See in the Dark: People Watch Body Movement in Pitch Black Conditions

First Posted: Oct 31, 2013 11:17 AM EDT

Can you see in the dark? Most people assume that they can't. New research, though, may show otherwise. It turns out that most humans can see their body's movement in total darkness, revealing a little bit more about vision and human perceptiveness.

"Seeing in total darkness? According to the current understanding of natural vision, that just doesn't happen," said Duje Tadin, one of the researchers, in a news release. "But this research shows that our own movements transmit sensory signals that also can create real visual perceptions in the brain, even in the complete absence of optical input."

In order to examine how well people might be able to see in the dark, the researchers conducted five different experiments involving 129 individuals. The real challenge of this study, though, was to measure objectively a perception that is, at its core, subjective. Could people really see their own moving hand in the dark, or were they just telling researchers what they thought they wanted to hear? That's why the scientists tracked eye movements. They also employed synesthetes. These people experience a blending of their senses in daily life; for example, individuals may see colors when they hear music or even taste sounds.

The researchers tracked the eye movements of the participants and took reports from the volunteers. Reports of the strength of visual images actually varied widely among participants, but synesthetes were strikingly better at not just seeing movement, but also experiencing clear visual form. As an extreme example in the eye tracking experiment, one synesthete exhibited near perfect smooth eye movement as she followed her hand in darkness.

"You can't just imagine a target and get smooth eye movement," said David Knill, one of the researchers, in a news release. "If there is no moving target, your eye movements will be noticeably jerky."

This particular link with synesthesia also reveals new insight when it comes to our self-awareness. It suggests that our human ability to see self-motion is based on neural connections between the senses. In fact, it shows that synesthesia may involve many areas of atypical brain processing.

So can we really see in the dark? It's more likely that the participants are basing their observations on experience.

"Innate or experience? I'm pretty sure it's experience," said Tadin in a news release. "Our brains are remarkably good at finding such reliable patterns. The brain is there to pick up patterns--visual, auditory, thinking, movement. And this is one association that is so highly repeatable that it is logical our brains picked up on it and exploited it."

The findings are published in the journal Psychological Science.

Want to learn more about the experiment? Check out the video below, courtesy of YouTube.

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